As conventional image display devices, there are known flat panel displays such as a liquid-crystal display (LCD), a plasma display, and an organic EL display (refer to, for example, “Thorough comparison of LCD, PDP, and organic EL display,” Kogyo Chosakai Publishing, Inc.).
The LCD displays an image by applying voltages to the liquid crystal to change the orientation thereof and blocking or transmitting light from a light source such as a backlight using a polarizing filter. The LCD, however, has problems such as a low response speed which is caused by the time required for the orientation change of the liquid crystal, a narrow view angle, a low contrast in a dark place, high power consumption which is caused by a requirement for some backlight luminance (for example, 10000 cd/m2) to secure display luminance due to low optical transmittance, from the principle of the liquid crystal. Moreover, a high-definition LCD has a problem of high power consumption caused by a requirement for a higher luminance backlight due to a decrease in size of pixels of the display.
Furthermore, the plasma display displays an image by discharging in a cell filled with Xe gas, exciting RGB phosphors using ultraviolet rays in the vacuum ultraviolet region (140 nm), and forming display pixels. Accordingly, the plasma display has problems such as too large pixels inappropriate for a small-sized display, a short lifetime which is caused by the light in the vacuum ultraviolet region having large light energy of 7 to 8 eV that inevitably leads to deterioration of the phosphors applied or evaporated in the pixels, and high power consumption during operation which is caused by a low energy conversion efficiency of a conversion from the ultraviolet rays in the vacuum ultraviolet region to visible light.
Moreover, the organic EL display displays an image by applying or evaporating an organic light-emitting material that emits light by voltage application onto a substrate having optical transparency and then applying a DC voltage. Due to the properties of the organic light-emitting material, the organic EL display has problems such that: the lifetime of the organic light-emitting material is not secured; the organic light-emitting material is extremely sensitive to humidity; power consumption is high since there is no efficient organic light-emitting material; it is difficult to form a film of the organic light-emitting material uniformly over a large area; and the organic light-emitting material is expensive.